The invention relates to an endoscope with a shaft that houses a lighting and image transmission system, the endoscope being designed to be autoclavable.
Endoscopes of this kind are widely known and are used in minimally invasive surgery. In rigid endoscopes, the shaft is made of a stiff material, in most cases medical-grade steel. In flexible endoscopes, the shaft, at least in the flexible area, is made of a pliant plastic material.
The shaft of the endoscope comes into direct contact with the tissue during use and is thus exposed to contamination. For economic reasons, it is of advantage to be able to use such endoscopes more than once.
For this purpose, the endoscopes initially have to be cleaned after use and thereafter have to be sterilized, this usually being done by an autoclaving process.
In autoclaving, the endoscope is exposed to relatively high temperatures. In what is called flash autoclaving, it is exposed to temperatures of over 134° to 165° C. In addition, chemicals, for example peroxide-containing chemicals, are sometimes added to the autoclave, in order to achieve absolute sterility.
As minimally invasive surgery is becoming increasingly more common, these cycles are being carried out several times a day, with the result that such endoscopes are exposed to considerable stresses, which they have to be able to withstand over a long period.
In rigid endoscopes, this can be achieved by using suitable metals.
In flexible endoscopes, this cannot be achieved with any great certainty, since the flexible materials, mostly plastics, do not withstand these harsh conditions over the long term. However, the flexibility allows the operator much greater viewing ranges, specifically since the distal end can be curved, resulting not only in a straight-ahead view but also in an all-round lateral view.
In rigid endoscopes, the distal end has suitably bevelled lenses in order to permit not only a straight-ahead view (0° view) but also angled oblique views of up to 45°.
There is a need, however, for autoclavable endoscopes that permit a flexible viewing direction.
U.S. Pat. No. 5,402,768 discloses designing the shaft of an endoscope in such a way that an inner shaft core houses the optical elements of the image transmission system. These can be conventionally rigid glass lenses or, in more modern constructions, imaging elements in the form of semiconductor image sensors (CCD, CMOS). The incident image is reflected via a lens onto the semiconductor image sensor and is converted there into electrical signals that are routed through cables in the inside of the shaft to the proximal end of the endoscope. These signals are then processed and are in most cases displayed as an image on a monitor. Since the structural units of a semiconductor image sensor are getting ever smaller, they can be used in particular in flexible endoscopes, since a curvature of the shaft does not impair these small structural parts.
However, the problem of autoclaving arises here.
In U.S. Pat. No. 5,402,768, this problem is remedied by a tubular cover being pushed over the inner core of the shaft so as to completely cover the latter and seal it hermetically at the distal end. At the proximal end, the tube even has bellows-like folds that can be pulled for protection over the whole proximal end area of the shaft, and thus also of the endoscope.
As a result, the shaft itself no longer comes into contact with the tissue during an intervention, only the outer sleeve that has been pushed over it.
After one use, the sleeve is removed again and discarded.
In one embodiment, control wires are integrated in the outer sleeve and can be used to curve the assembly of flexible shaft and outer flexible sleeve.
This endoscope is awkward to handle, since the sterile tube has to be pushed onto the long thin shaft of the endoscope before each use, and this requires a certain skill. It is not possible to exclude the possibility of the shaft being contaminated during these preparatory manoeuvres.
The risk of contamination is much greater when, after use, the tube is removed again from the shaft and discarded. It is therefore necessary for the inner core, which contains the image transmission system, to be sterilized by disinfecting liquids. However, these procedures are very time-consuming and, after a large number of uses, there is the possibility of the aggressive chemical substances passing through the plastic wall of the core and penetrating into the interior of the core.
The object of the present invention is therefore to make available an autoclavable endoscope that is deflectable and is easy to handle.